This invention is directed to assembly apparatus and methods of assembly of strain indicators, fluid type and non-fluid type. The preferred embodiment of this invention is directed to the assembly of fluid strain indicators of the general type disclosed in the patents and applications referenced above under the heading "Cross Reference to Related Applications and Patents". It should be appreciated, however, that the apparatus and methods of this invention are not solely limited to the structures shown and described in the patents and applications referenced herein. Rather, the referenced applications and patents are cited merely for the purpose of illustration to demonstrate the application of the assembly apparatus and methods of this invention. The invention is also applicable to the assembly of non-fluid type strain indicators as will be described below.
Fluid filled strain indicators of the type shown in the applications and patents referenced above operate on a principle that the application of stress to a strain or tensile member causes an elongation or deflection to take place in the tensile member. If a fluid filled capsule including a window and an indicator area is advantageously positioned relative to the tensile member, the change in length or deflection encountered in the tensile member after a load has been placed on such member can be translated into movement of the indicator area with respect to the window. As a result the change in length of the tensile member or deflection thereof can be visually observed thus giving confirmation as to the load condition of the tensile member.
Total movement of the indicator area with respect to the window of strain indicators of the type referenced above is very slight being on the order of 0.001 inches. That is to say as the tensile member is placed under load movement of the indicator area with respect to the window from a no load to a design load condition is on the order of magnitude of 0.001 inches. It can therefore be appreciated that the tolerances required in the manufacture and assembly of strain indicators of this type are quite close. Dimensional inaccuracies of the smallest degree can either produce an erroneous or false reading as to the load condition of the tensile member or no reading at all.
This invention is directed to assembly apparatus and assembly methods by means of which strain indicators may be assembled on a production line basis and wherein individual testing and evaluation of each indicator is accomplished as assembly takes place.
This invention further provides for assembly apparatus and methods by means of which dimensional variations and inaccuracies in the individual components of the indicator can be effectively compensated for in assembly.